JPH06185534A - Fixing structure of joint boot - Google Patents

Abstract

PURPOSE:To provide fixing structure wherein leakage of grease is prevented from occurring and entrance of dust is prevented from occurring by modifying the fixing structure of a joint boot having ozone resistance and bending fatigue resistance. CONSTITUTION:A thermoplastic polyester elastomer composition wherein 80-1wt.% rubber is blended in 20-90wt.% a thermoplastic polyester elastomer is formed on a bellows-form cylinder body having a difference between bores at two end parts. Shafts 3 and 4 are inserted in the large and small bore parts 1 and 2, respectively, of the joint boot. The outer peripheries thereof are securely fastened by means of a band 5 made of a steel and a difference in diameter between diameters before and after fastening of the large bore end part 1 is adjusted to 0.3-2.5mm and a difference in diameter between diameters before and after fastening of the small bore part 2 is adjusted to 0.3-2.5mm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a joint accessory such as a constant velocity joint for automobiles, and relates to a joint boot fixing structure for dustproofing or grease encapsulation.

[0002]

2. Description of the Related Art Generally, a joint portion for an automobile or an industrial machine holds a grease enclosed therein,
In addition, boots made of an elastic material such as rubber are attached to prevent dust.

As shown in FIG. 1, such a joint boot has a cylindrical bellows structure having caliber differences at both ends. The joint boot has a large caliber end 1 and a small caliber end 2. The drive shaft 3 and the driven shaft 4 are inserted, and the outer peripheries of the drive shaft 3 and the driven shaft 4 are fastened and fixed by bands 5.

As for the band 5, as shown in FIG. 2, a steel plate having a wall thickness of about 0.4 mm and a width of about 7 mm is curved and spot-welded by leaving an extended portion 6 at one end thereof. It is a ring. In order to tighten and fix the outer periphery of the joint boot with such a band 5, the extension portion 6 is folded back as shown by the arrow, and the pair of upright pieces 8 attached to the key points of the ring are bent to extend the extension portion. Fix 6 by stacking.

The molding material for such a joint boot is being converted from chloroprene rubber into a thermoplastic polyester elastomer in order to meet recent demands for ozone resistance and flex fatigue resistance, and physical properties improved in aging resistance. Have.

[0006]

However, since the joint boot molded from the above-mentioned conventional thermoplastic polyester elastomer has low flexibility and a large compression set, the conventional band is sufficient. There is a problem that it is difficult to fix with a sufficient tightening force.

Therefore, the present invention solves such a problem, improves the fixing structure of the joint boot having ozone resistance and bending fatigue resistance, and more reliably with a commonly used annular band. It is an object to prevent the grease from leaking by sealing it to and to prevent the intrusion of dust.

[0008]

In order to solve the above-mentioned problems, in the present invention, a thermoplastic polyester elastomer composition obtained by blending 20 to 99% by weight of a thermoplastic polyester elastomer with 80 to 1% by weight of rubber is prepared. Joint boots are molded into bellows-shaped tubular bodies with different diameters, and shafts are inserted into the large-diameter end and small-diameter end of the joint boot, and the outer circumferences of the joint boots are tightened with bands, respectively. The means for fixing the end portion has a diameter difference of 0.3 to 2.5 mm before and after fastening and the small diameter end portion has a diameter difference of 0.3 to 2.5 mm before and after fastening. .

[0009]

The fixing structure of the joint boot according to the present invention comprises a joint boot having ozone resistance and flex fatigue resistance, which is formed from a thermoplastic polyester elastomer composition containing a thermoplastic polyester elastomer and rubber in a predetermined ratio, With the annular band that is used, the diameter difference between the large diameter end and the small diameter end before and after fastening is tightened to the specified size, so the sealing condition becomes more reliable, and therefore oil leakage and dust intrusion are possible. Can be reliably prevented.

[0010]

The joint which is the member to which the joint boot is attached in the present invention is not particularly limited to a constant velocity joint, and generally, a connecting portion between a drive shaft and a wheel in an automobile or an industrial machine, and transmission of a driving force. It may be a universal joint forming a system.

The thermoplastic polyester elastomer used in the present invention is a block copolymer comprising a high melting point polyester segment and a low melting point polymer segment. The low melting point polymer segment has a molecular weight of 400 to 60.
The melting point may be 00, and the upper limit of the melting point is not particularly limited, but is generally 130 ° C. or lower, preferably 100 ° C. or lower. The softening point of the thermoplastic polyester elastomer is particularly preferably 100 ° C. or lower.

The aromatic polyester unit of the high melting point polyester segment which is the hard segment is composed of an acid component and a glycogen component, and the acid component is substantially terephthalic acid or 2,6-naphthalenedicarboxylic acid or these. It is a combination product of. Along with the above-mentioned terephthalic acid or 2,6-naphthalenedicarboxylic acid, other aromatic dicarboxylic acid such as isophthalic acid,
Or adipic acid, sebacic acid, cyclohexane-1,
Aliphatic dicarboxylic acids such as 4-dicarboxylic acid and dimer acid may be used together in small amounts.

On the other hand, the glycogen component constituting the aromatic polyester unit is a glycol having 2 to 12 carbon atoms, such as ethylene glycol,
Propylene glycol, tetramethylene glycol, neopentyl glycol, hexanediol, decanediol and the like.

The low melting point polymer segment which is a soft segment is composed of an aliphatic polyether unit and an aliphatic polyester unit, and one aliphatic polyether unit is formed of polyalkylene glycol. Specific examples of the polyalkylene glycol include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polyethylene glycol-polypropylene glycol block copolymer, and the like, and polytetramethylene glycol is particularly preferable. Such a polyalkylene glycol can be used alone or as a mixture as long as the ratio of the number of carbon atoms to the number of oxygen is 2 to 4.5.

The other aliphatic polyester unit constituting the low melting point polymer segment is mainly composed of an aliphatic dicarboxylic acid and glycol, and the main acid component of the aliphatic dicarboxylic acid is, for example, succinic acid, adipic acid, These include sebacic acid and decanedicarboxylic acid, and a small amount of aromatic dicarboxylic acid such as isophthalic acid may be used together. The glycol component may be the same compounds having 2 to 12 carbon atoms and exemplified as the glycol component forming the aromatic polyester unit of the high melting point crystalline segment. Such an aliphatic polyester unit is obtained by polycondensing the above aliphatic dicarboxylic acid and a glycol component by a usual method, and may be a homopolyester or a copolyester, or a ring-opening polymerization of a cyclic lactone. It may be a polylactone (for example, poly-ε caprolactone) obtained by the above.

The composition ratio of the high melting point crystalline segment and the low melting point polymer segment in the above thermoplastic polyester elastomer is preferably 95: 5 to 5: by weight.
The range is 95, more preferably 70:30 to 3
The range is 0:70.

The polyester block copolymer particularly preferably used as the thermoplastic polyester elastomer is a low melting point polymer using polytetramethylene terephthalate or polytrimethylene terephthalate-2,6-naphthalate as the high melting point crystalline segment. The segment is formed by using a polyether such as polytetramethylene glycol, a polyester such as polytetramethylene adipate, and poly-ε-caprolactone. In addition, polycarboxylic acid or polyfunctional hydroxy compound as a part of dicarboxylic acid or glycol,
It may be a copolymer of oxyacid and the like. Examples of the polyfunctional component include trimellitic acid, trimesic acid, pyromellitic acid, benzophenonetetracarboxylic acid, butanetetracarboxylic acid, glycerin, pentaerythritol, their esters, and acid anhydrides. Copolymerization of these polyfunctional components in an amount of 3 mol% or less effectively acts as a viscosity increasing component.

As a polymerization method for producing the above-mentioned thermoplastic polyester elastomer, a well-known polymerization method can be adopted. A preferable polymerization method is aromatic dicarboxylic acid or its dimethyl ester and a low melting point segment forming property. Diol and about 150-260 in the presence of a catalyst
A method of obtaining a thermoplastic elastomer by heating to ℃, carrying out an esterification reaction or transesterification reaction, and then carrying out a polycondensation reaction while removing excess low-molecular diol under vacuum, formation of a pre-adjusted high-melting polyester segment Prepolymers and low melting point polymer segment-forming prepolymers are mixed with difunctional chain extenders that react with the end groups of those prepolymers and the system after reaction is kept at high vacuum to remove volatile components. Thus, a method of obtaining a thermoplastic polyester elastomer, a method of obtaining a thermoplastic polyester elastomer by subjecting a high-melting point polyester having a high degree of polymerization and a lactone to heat-mixing, and performing an ester exchange reaction while ring-opening polymerization of the lactone, etc. Can be mentioned.

As the rubber used in the present invention, various synthetic rubbers or natural rubbers can be used alone or in combination of plural kinds. Examples of preferable rubber materials include polar diene rubbers and hydrogenated products thereof, acrylic rubbers, hydrin rubbers, urethane rubbers, chlorophosphazene rubbers, thermoplastic polyurethane elastomers and thermoplastic polyamide elastomers. Further, silicone rubber and fluororubber are also preferable in terms of oil resistance. Particularly preferred rubbers are non-halogen diene rubbers and hydrogenated products thereof,
Examples thereof include epichlorohydrin rubber, and specifically, acrylonitrile-butadiene copolymer rubber, hydrogenated acrylonitrile-butadiene copolymer rubber, hydrogenated acrylic ester-butadiene copolymer rubber, ethylene-propylene copolymer rubber and the like.

The compounding ratio of the above rubber in the thermoplastic polyester elastomer composition is such that the thermoplastic polyester elastomer component (hereinafter referred to as A component): the rubber component (hereinafter referred to as B component) = 99 to 20: 1 to 80 ( % By weight), preferably 95-51: 5-49 (% by weight), and more preferably 85-55: 15-45.
(% By weight). This is because when the amount of the component A used exceeds the predetermined range, the amount of the component B used becomes insufficient, and as a result, the flexibility and compression set of the resulting thermoplastic polyester elastomer cannot be sufficiently improved. When the amount of the component A used is less than the predetermined range, the thermoplastic polyester elastomer obtained has poor processability and fluidity.
If it is less than weight%, injection molding is difficult.

The thermoplastic polyester elastomer composition used in the present invention can be obtained by simply blending the above-mentioned component A and component B. However, when it is dynamically crosslinked, it becomes a composition having further excellent performance.

The term "dynamic cross-linking" as used herein means Uniroyal.
W. M. Fischer et al. And A. from Monsanto. Y. Is a method developed by Coran et al.
It means that rubber is blended in a matrix of a thermoplastic resin, the rubber is highly crosslinked while being kneaded with a crosslinking agent, and the rubber is finely dispersed. The cross-linking agent used for such dynamic cross-linking may be a known one such as a peroxide used for ordinary rubber, a resin cross-linking agent, and sulfur. For example, "Crosslinking Agent Handbook (Shinzo Yamashita,
Kaneko Tosuke, Taiseisha), preferably 1,3-di (t-butylperoxyisopropyl).
Benzene, 2,5-dimethyl-2,5-di (t-butylperoxine) hexane, 2,5-dimethyl-2,5-
Examples thereof include di (t-butylperoxine) hexine and t-butylcumyl peroxide.

The amount of the above-mentioned crosslinking agent added is not constant depending on the required performance of the thermoplastic polyester elastomer composition and the type of the crosslinking agent, but is usually 0.01 to 8 parts by weight with respect to 100 parts by weight of the rubber. is there. This is because even if the amount exceeds 8 parts by weight, the crosslinking reaction does not proceed any further, and rather adverse effects such as decomposition of the polymer occur, and if it is less than 0.01 parts by weight, the crosslinking reaction does not sufficiently occur. .

The thermoplastic polyester elastomer composition was subjected to dynamic crosslinking in this way, its hardness _{H D: 20~44points (H s:} 60~95po
ints), and the tensile elastic modulus is 400 kgf / cm ²
And become soft. Incidentally, the hardness of the thermoplastic polyester elastomer is, H _D: 45 or more (H _s: 96 or more)
And the tensile elastic modulus at room temperature (23 ± 5 ℃) is 600kgf.
/ Cm ² or more. And the tensile elastic modulus is 50 to 39.
If the thermoplastic polyester elastomer composition is 0 kgf / cm ² , the joint boot can be easily fastened and fixed using a simple metal band (see FIG. 2).

The tensile breaking strength of the thermoplastic polyester elastomer composition of the present invention is preferably 50 to 50.
300 kgf / cm ² , and more preferably 60 to ²
80 kgf / cm ² , more preferably 70 to 250 k
It is gf / cm ² . This is because insufficient strength is less than 50 kgf / cm ^2, in the case of exceeding 300 kgf / cm ² and it is necessary to suppress the rubber content as much as possible, because no sufficient flexibility is obtained. The compression set of the composition is 80% or less (JIS K-6301, 120).
(° C 22 hours) is preferable, and more preferably 75%
The ratio is particularly preferably 70% or less. This is because if it exceeds 80%, the joint between the small diameter end of the joint boot and the shaft is not sufficiently fixed.

In the present invention, the difference in diameter of the large-diameter end portion before and after fastening is preferably 0.3 to 2.5 mm, more preferably 0.5 to 2.2 mm, and the small-diameter end portion. The difference in diameter before and after fastening is preferably 0.3-
2.5 mm, more preferably 0.5 to 2.2 mm
To be fixed. The diameter of the large-diameter end of the constant velocity joint of an automobile is usually 67 to 10 before fastening.
It is about 7 mm, and the diameter of the small diameter end is 25 to 3 similarly.
Although it is about 8 mm, regardless of such a size aspect, if the diameter difference between the large diameter end portion before and after fastening is less than 0.3 mm, grease leaks from the inside of the boot during joint rotation, resulting in insufficient sealing. If the diameter is larger than 2.5 mm, it is not preferable because fastening with bare hands becomes impossible. If the diameter difference between the small-diameter end portion before and after fastening is less than 0.3 mm, grease leaks from the inside of the boot during joint rotation, resulting in insufficient sealing. If it exceeds 2.5 mm, fastening with bare hands is not possible. It is not possible because it becomes possible.

[Experimental Example] Thermoplastic polyester elastomer (manufactured by Enchem Polymeri: PIBIFLEX 4)
6M) (hereinafter abbreviated as TPEE), acrylonitrile butadiene rubber (manufactured by Japan Synthetic Rubber Co., Ltd .: JSR NBR)
N230SV) (hereinafter abbreviated as NBR), auxiliary agent (manufactured by Ouchi Shinko Co., Ltd .: Barnock PM), P.I. O (Kaya Hexa AD manufactured by Kayaku Akzo Co., Ltd.) was mixed in the proportion shown in Table 1,
The composition 3 was kneaded only at 210 ° C. at a rotation speed of 200 rpm using a twin-screw extruder, and the composition 1 and the composition 2 were mixed under the same conditions while adding a crosslinking agent, Crosslinking was performed to prepare pelletized compositions. After thoroughly drying the obtained pellets,
Molded into a sheet having a thickness of 2 mm with an injection molding machine under the condition of 210 ° C., and various physical property tests as shown below are performed.
The results are also shown in Table 1. In addition, when TPEE alone was used as the composition 4, its physical properties are also shown in Table 1.

(1) Fluidity (MFR) (g / min): 23
0 ° C, 10 kg (2) Hardness H _S : JIS K-6301 JIS A
Hardness (3) Hardness H _D: ASTM _D-2240 Shor
e D hardness (4) Tensile strength T _B (kgf / cm ² ): JIS K
-6,301 JIS 3 dumbbell (5) Tensile elongation _{E B (%): JIS K} -6301
JIS No. 3 dumbbell (6) Tensile elastic modulus (kgf / cm ² ): The value of the dynamic tensile elastic modulus (E) was obtained by the forced vibration non-resonance method at 23 ± 2 ° C. The width is about 2 mm, the thickness is about 1 mm, and the length is about 30.
mm test piece, frequency 10Hz, displacement amplitude 3μm
The dynamic stress, the dynamic displacement, and the phase angle were determined by applying the sinusoidal strain of, and calculated by the following formula.

[0029]

[Equation 1]

In the formula, CD: length of test piece, DF: dynamic stress, DD: dynamic displacement, P: phase angle, W: width of test piece,
T: Thickness of the test piece.

(7) Heat aging resistance (%): JIS K-6
301 using a gear type aging tester at 120 ℃ 30
The tensile strength after 0 hours was measured, and the change rate (%) with respect to the tensile strength before the heat resistance test was shown.

(8) Oil resistance (%): JIS K-630
1 The tensile strength after immersion in JIS No. 3 oil at 120 ° C. for 70 hours was measured, and the change rate (%) with respect to the tensile strength before the oil resistance test was shown.

(9) Abrasion resistance (10 ³ times mg): AST
MD-1044 Tapered Wear CS-17 Wheel 1
000g weight (10) Compression set (%): JIS K-6301 12
0 ° C for 22 hours

[0034]

[Table 1]

On the other hand, the compositions 1 to 3 of the examples shown in Table 1 were injection-molded under the following conditions to form joint boots having the shape shown in FIG. Note Screw speed: 100 rpm, Cylinder temperature: 21
0 ℃, nozzle temperature: 210 ℃, injection pressure: 800kgf
/ Cm ² , injection time: 2 seconds, cooling time: 20 seconds, mold temperature: 40 ° C., and a joint boot made of the obtained compositions 1 to 3 is shown in FIG.
In the state shown in (4), it was attached to an automobile constant velocity joint and the tightening property and sealing property when fixed were examined.

As shown in FIG. 2, the band used in this case is formed by bending a steel plate having a thickness of 0.4 mm and a width of 7 mm and fixing it by spot welding 7, leaving an extension 6 at one end thereof. It is a ring. To tighten and fix the outer circumference of the joint boot with the band 5 as described above, the extended portion 6
Was folded back as shown by the arrow and tightened, and a pair of upright pieces 8 attached to the key points of the ring were bent to overlap and fix the extended portion 6.

Regarding the result of the tightening property, when the diameter difference before and after fastening the large diameter end and the diameter difference before and after fastening the small diameter end are both set to 0.1 mm intervals of 0.2 to 2.6 mm. In the case of, it can be easily tightened with bare hands, and the band is broken using a crimping jig.
The mark was evaluated in two stages. Regarding the sealing property, the boot should be filled with grease and the ambient temperature should be -5.
A continuous operation was carried out for 50 hours under the conditions of ℃, joint operating angle of 30 deg and rotation speed of 400 rpm. The results in this case were evaluated as ◯ when the grease did not leak after 50 hours, and as x when the grease did not leak after 50 hours.

[0038]

[Table 2]

[0039]

[Table 3]

As is clear from the results shown in Tables 2 and 3, the diameter difference before and after fastening the large diameter end portion is 0.3 to 2.5 m.
m, and the diameter difference before and after fastening the small diameter end is 0.3.
Only when the thickness was 2.5 mm, the desired effects such as excellent assembling property and sealing property were obtained.

[0041]

As described above, according to the present invention, when the outer peripheries of both ends of the joint boot molded from the thermoplastic polyester elastomer composition are fastened with bands, the difference in diameter before and after fastening becomes a predetermined dimension. Since it is fixed like this, the fixing structure of the joint boot that satisfies the requirements of ozone resistance and bending fatigue resistance is improved, and it is sealed with an annular band that can be attached with simple operation,
There is an advantage that it is possible to more reliably prevent oil leakage and dust intrusion.

[Brief description of drawings]

FIG. 1 is a partially cutaway side view showing a constant velocity joint equipped with joint boots.

FIG. 2 is a perspective view showing a fixing band.

[Explanation of symbols]

 1 Large diameter end 2 Small diameter end 3 Drive shaft 4 Driven shaft 5 Band 8 Standing piece

Claims (1)

[Claims] 1. A thermoplastic polyester elastomer 20.
A thermoplastic polyester elastomer composition containing 99 to 99% by weight of rubber and 80 to 1% by weight of rubber is molded into a bellows-shaped tubular body having different diameters at both ends to form a joint boot,
A shaft is inserted into each of the large-diameter end portion and the small-diameter end portion of the joint boot, and the outer circumference thereof is tightened with a band so that the diameter difference between before and after fastening the large-diameter end portion is 0.3 to
A fixing structure for a joint boot, which is fixed to have a diameter of 2.5 mm and a diameter difference before and after fastening of the small-diameter end portion to be 0.3 to 2.5 mm.